Blister packages are used for a variety of purposes including packaging of small items such as pharmaceuticals, electronics, contact lenses, among others. These packages typically consist of a blister tray having a recessed portion and shoulder portions, and a lidding sheet that is adhered to the blister tray portion. In some cases, an intermediary adhesive sheet is also included between the lidding sheet and the blister sheet.
In various applications, the lidding sheet is provided with an adhesive in order to adhere to the blister tray. This, however, is problematic when the lidding sheet also needs to be capable of being printed on. Running a lidding sheet through a printer, where the lidding sheet includes an adhesive, could jam the printer or could ruin the printer by leaving adhesive within the printer. Alternatives to this include: providing a layer over the adhesive, which can be peeled away prior to the adhesion of the blister tray to the lidding sheet. However, this results in a very thick lidding sheet that makes it difficult to access the blister. In order to facilitate access to the blister container, perforations are often added to the lidding sheet, which could result in the loss of a hermetic seal for some applications.
Other options include the adding of an adhesive to the blister tray itself and having a cohesive bond between the blister tray and a lidding sheet. An example is U.S. Pat. No. 5,014,851 to Wick. Wick discloses the addition of a cohesive to the blister tray either prior to or after the formation of the blister recesses. In the case of adding a cohesive prior to the formation of the blister recesses, a problem with Wick is that the cohesive could affect the transparency of the blister recess when the blister is formed. Further a problem with having the cohesive within the blister recess area is that it could contaminate the product within the blister recess.
Conversely, in Wick, if the coating is applied after the formation of blister, no system is presented for this. If the process of adding an adhesive through rollers is used on the formed package, the problem with Wick is that a non-uniform coating of adhesive is applied to the shoulders of the blister tray since the blister tray is not completely rigid, thus potentially causing non-uniformity of coating and areas of non-coated shoulders. Further, the cohesive could also leak into the blister recess area under this system.